Endometriosis is the occurrence of endometrial tissue in places other than the uterus. This condition is associated with pelvic pain, infertility, and excessive bleeding during menstruation. Endometriosis is generally diagnosed by a visual inspection of the peritoneal cavity. However, there is growing evidence that simple visual inspection of the peritoneal cavity is a poor technique for the diagnosis of endometriosis, especially since many of the lesions are microscopic in size.
Recently, a diagnostic technique has been developed for the use of hematoporphyrin-derivatives (HPD), drugs which concentrate in cancer cells. Because this drug is selectively retained by proliferating tissues, it can be used as a "tumor-specific" marker. When tissue is irradiated with light having a wavelength of approximately 405 nanometers, cells containing HPD produce fluorescent radiation, which can be used to assist the physician in locating cancerous tissue. In addition, HPD has a cytotoxic effect by inducing the release of an oxygen singlet when the cells are irradiated with light in the wavelength range of 630 nm. This latter phenomenon can be used in the treatment of the cancerous tissue. The HPD diagnostic and treatment technique employing multiple radiation sources is shown generally in U.S. Pat. Nos. 4,541,438; 4,576,173; and 4,592,361 issued to Parker. In addition, U.S. Pat. No. 4,336,809, issued to Clark, shows the use of a single laser, which produces light at two wavelengths, as the energy source for both the diagnosis and treatment of HPD-marked cells.
Despite its utility for locating cancerous cells, the HPD diagnostic technique has a number of problems. For example, the timing between the administration of the drug and the diagnosis is critical (approximately 48 hours). In addition, the HPD makes the patient photosensitive, thus creating a risk of possible phototoxic side effects. For example, photosensitizers such as HPD are capable of intra-ocular penetration through the blood aqueous and blood-retina barrier and may subsequently degrade the ocular lens and retina on exposure to ultraviolet light (200-400 nm). Therefore, patients undergoing HPD diagnostic treatments usually must be isolated for several days in a dark room to prevent undesired photosensitivity reactions.